1. Field of the Invention
As lead additives are removed from gasoline, there is a continuing need for higher octane gasoline blending components. A primary means of obtaining these higher octane gasoline components is catalytic reforming. Catalytic reforming has undergone dramatic improvements in octane capability, operating efficiency, and selectivity in yield and product quality in the past six years. However, to meet the increasingly rigorous specifications for gasoline, in an economic and efficient manner, new approaches are required.
This invention is directed to a process whereby the increasingly rigorous quality specifications for gasoline, inter alia, octane numbers, volatility, specific gravity, aromatics content, lead antiknock compound content, can be met. Further, the gasoline produced meets all the general requirements associated with providing for satisfactory engine performance, particularly those requirements necessary for proper performance of (1) highcompression engines, and (2) engines whose design induces at certain times incomplete fuel vaporization and subsequent unequal distribution of fuel components to all combustion chambers. These general requirements for gasoline quality are well known to those skilled in the practice of refining naphthas to produce high quality gasolines. Of current and future concern, especially to refiners in Europe and Japan and increasingly to U.S. gasoline producers, are those additional aforementioned requirements which include, but are not limited to, high front end octane number, minimum density or specific gravity, and minimum percent evaporated or distilled at temperatures of 200.degree. F. to 225.degree. F. Typical of premium grade gasoline specifications to meet these additional requirements are:
1. R-100 O.N. (front end octane number) -- 89.0 to 91.0 minimum PA1 2. Specific gravity -- 0.745 to 0.750 minimum PA1 3. Volume percent distilled at 212.degree. F. -- 44 to 50 percent minimum; PA1 Research octane number -- 97 to 99 minimum PA1 Motor octane number -- 86 to 90 minimum PA1 Aromatics content, volume percent -- 45 to 52 maximum PA1 Lead content, gm Pb/U.S. Gal. -- 0 to 2.0 maximum. PA1 a. a first fraction comprising C.sub.4 .sup.- hydrocarbons, and preferably iC.sub.5, and PA1 b. a second fraction comprising C.sub.5.sup.+ hydrocarbons:
In conjunction with general specifications of:
While typical of specifications for premium grade gasolines, these values should not be construed as limiting since more or less severe specifications may be set up dependent on a variety of factors.
To meet the above specifications (1), (2) and (3) requires processing to upgrade the octanes of the C.sub.5 --C.sub.6 --C.sub.7 components of naphthas, preferably the C.sub.6 -C.sub.7 components, and more preferably the C.sub.7 components. Correspondingly the processing may provide a degree of upgrading by removal of the lowest octane components by conversion to lighter-than-gasoline materials, e.g., propane, which results in a higher octane number gasoline. It is common practice to upgrade octanes of C.sub.5 --C.sub.6 --C.sub.7 components by isomerization, reforming, separation by distillation or extraction, and various other well known processing steps sequentially and in various combinations. The complexity and cost of these combinations increase in proportion to the required overall octane upgrading. It is the purpose of this invention to provide a simple, direct and economical process for producing gasoline meeting all of the aforesaid quality requirements, and especially and uniquely maximizing the octanes of the C.sub.5 --C.sub.6 --C.sub.7 portions of gasoline while yielding the correct proportions of C.sub.5 --C.sub.6 --C.sub.7 to satisfy specific gravity and volatility requirements.